Manufacturing, warehousing and large retail businesses are always faced with the problem of moving and storing their inventory, whether for a short period of time before shipping or for longer periods of time prior to usage or sale. Furthermore, many manufacturing concerns, particularly in the automotive industry, now operate on the "just-in-time" principle, which means that component parts from other parts of the plant or from outside suppliers are delivered to an assembly area with minimal storage flow just before they are to be used. No matter how a business operates, if it accumulates, stores or uses inventory it will be faced with the problem of moving and storing that inventory and of ensuring that the inventory is retrieved and used in the correct sequence. Computerized inventory control is now the norm, especially in "just-in-time" manufacturing situations and it is now essential that any system in which inventory is to be placed be adaptable to computer control. It is also essential that inventory storage and retrieval systems be economical to purchase and operate.